Good book on trigonometry proofs?

I'm looking for a decent, (and preferably cheap) book, or books, on trigonometry. Something that proves some or all the trig equations we're expected to remember in high school stuff (most of which I've forgotten), but it should also leave room for my curiosity so I can prepare for higher level college courses in geometry. If it included triangles and circles on the complex plane, that would be a plus.

Gelfand is a real mathematician and his trig book is a rigorous treatment of the subject, with challenging questions. It includes triangles and circles, and proves all things triangle like pythoagorean theorem and ptolemy's theorem, even triangle similarity theorems. Nothing on the complex plane though. All the trionometric relations are stated and proved. It is also cheap, at $30. It looks like it meets your criteria:

Not sure if it is "good" or not, but I believe it is basically good; Trigonometry (not remember which edition) by Larson & Hostetler. You could find it cheap, used, from a library book sale. You can likely also find other truely good Trigonometry books from used book sales. The Larson & Hostetler book contains everything you would want in a semester course, including complex numbers, vectors, vector projections, some applications exercises in almost every section of the book. Yes, bunches of stuff on triangles, too.